Review of strategies for the fabrication of heterojunctional nanocomposites as efficient visible-light catalysts by modulating excited electrons with appropriate thermodynamic energy

Due to the gradual depletion of fossil fuel reserves on the earth and increasing pollution in the environment, it is highly desirous to develop renewable technologies for clean energy production and environmental remediation through extensively employing semiconductor photocatalysis. With regard to efficient photocatalysis, apart from charge separation, possessing sufficient thermodynamic abilities are the prerequisites so that the photogenerated electrons and holes can induce redox reactions. For most visible-light-responsive semiconductor photocatalysts, photogenerated holes exhibit strong oxidation ability because of their appropriate valence band top levels. However, the ability of the photogenerated electrons to induce reduction reactions is weak, generally due to their low conduction band bottom levels. Hence, a feasible strategy would involve the rational construction of a heterojunctional system with thermodynamically appropriate energy platforms as a space-separated electron shuttle for further intensifying the reduction reactions for efficient visible-light photocatalysis. Obviously, it is considerably meaningful to develop an appropriate electron energy platform-dependent efficient heterojunctional photocatalyst under visible-light irradiation and to review recent developments in this field. In this review, special emphasis is paid to bridged heterojunction-related advances made by our group, focusing upon visible-light-responsive single-metal oxides like Fe2O3, bimetal oxides like BiVO4, plasmonic noble-metal nanoparticles like Au, and polymer-based nanomaterials like g-C3N4 as model photocatalysts. Apparently, it is imperative to design efficient nanophotocatalysts for fields related to energy production and environmental remediation from the scientific and engineering points of view.